Treatment of wood tar distillate



Patented June 24, 1941 TREATMENT OF WOOD TAR DISTILLATE Alfred A.Camilli, Crystal Falls, and Malcolm K. Johnston, Marquette, Mich.,assignors to Cliffs Dow Chemical Company, Marquette, Mich, a

corporation of Michigan Application October 11, 1939,

N Drawing.

Serial No. 298,918

8 Claims.

This invention rel-ates to the treatment of wood tar distillate. Moreparticularly it concerns a new and improved inhibitor oil and a methodof preparing the same.

In the destructive distillation of wood, there is obtained, in additionto pyroligneous acid, an insoluble viscous material commonly termedsettled tar, which is usually separated into various fractions bydistillation at reduced pressure. One of these fractions, having anatmospheric boiling range of roughly 220-320 C., is known as inhibitoroil, and finds extensive use as a stabilizing agent for preventing gumformation in gasoline and like petroleum products. Unfortunately,however, inhibitor oil as ordinarily prepared develops after standing anappreciable proportion of dark reddish-brown coloring material ofunknown c nstitution, which lessens its desirability as an inhibitor.

In view of this disadvantage, an object of the present invention is toprovide a method of treating inhibitor oil to remove therefrom much ofthe objectionable dark reddish-brown coloring material.

This object is obtained by subjecting the inhibitor oil to the action ofan oxidizing agent and thereafter separating the substantiallyunoxidized fraction from the oxidized material, suitably bydistillation. The product so obtained is a straw-colored oil which hasan inhibiting power at least equal to that of ordinary inhibitor oil,and, even after long standing, develops very little reddish-browncoloring material. In addition, it is completely soluble in gasoline, asdetermined by the usual method. That is: three milliliters of the oil ina centrifuge tube are diluted to 100 milliliters with referencegasoline, and the sample is shaken thoroughly for ten minutes, and thencentrifuged for ten minutes, after which the volume of the oil layerremaining is measured to determine the percentage of insoluble material.

The exact nature of the chemical reaction occurring during the oxidativetreatment according to the invention is not understood. However, theoxidizing agent appears to attack preferentially the dark reddish-browncoloring materials and gasoline-insoluble bodies in the inhibitor oil,and to convert them to non-volatile tar-like substances from which theinhibitor oil can be separated by distillation or other means.

In so far as we have been able to determine, any oxidizing agent isoperable in the invention.

However, inorganic oxidizing agents, and particularly gaseous orvolatile liquid inorganic agents, such as oxygen, air, and hydrogenperoxide, are to be preferred because of the fact they leave no residuein the treated oil.

In a preferred mode of operating, the inhibitor oil and a smallproportion, usually 0.5 to 2.0 per cent, of the oxidizing agent aremixed and the mixture is stirred at a temperature of 20-50 C. forseveral hours, after which it is heated to a temperature of 120 C., forone or two hours. However, the oxidizing agent and oil may be allowed toreact under other conditions of time and temperature, preferably withinthe range 20-120 C. without departing from the invention. After theoxidation treatment, the resulting mixture is distilled, preferablythough not necessarily at reduced pressure, to recover the purifiedinhibitor oil as a yellow liquid, which dissolves completely in crackedgasoline (according to the solubility test pre-- viously outlined), andwhen present therein in a small proportion, e. g. 0.01 to 0.1 per centby weight, effectively retards gum formation.

Treatment according to the invention may also be accomplished byexposing the inhibitor oil in the vapor state to the action of theoxidizing agent, as during the distillation operation.

The following examples will illustrate the invention but are not to beconstrued as limiting its scope.

Example 1 A sample of inhibitor oil prepared by the vacuum distillationof hardwood settled tar, having an atmospheric boiling range of 230 C.-297" C., a specific gravity of 1.093 at 15.6 C./ 15.6 C., and a colordrop value of 22 (A. S. T. M. D-l5634T), was treated according to theinvention. A sample of the oil was placed in a closed iron pressurevessel and oxygen passed into the container until a gauge pressure ofpounds per square inch wa reached. The gas inlet was then closed and thevessel heated at 100 C. for three hours, during which time the gaspressure rose to pounds and then gradually dropped to 100 pounds. Theresultant treated oil was removed and distilled at reduced pressure, thedistillate being a yellow-colored inhibitor oil. having a color dropvalue of 30, which did not change appreciably even on long standing. Asmall proportion of tarry residue was left in the still.

Example 2 The untreated inhibitor oil of Example 1 was heated at atemperature of 100 C. for one hour mine water.

under oxygen maintained at a constant pressure of 20 pounds gauge, andwas then vacuum distilled. A light-yellow inhibitor oil was obtained.

Example 3 Example 4 A charge of ordinary inhibitor oil was heated at atemperature of 70 to 90 C. for 24 hours, during which time air was blowncontinuously through the hot oil. The product was then vacuum distilled,the distillate being a light-yellow inhibitor oil as in the recedingexamples.

Example 5 In a series of tests, ordinary inhibitor oil was mixed with asmall proportion of each of the following oxidizing agents: nitric acid,aqueous potassium permanganate, manganese dioxide, yellow mercuricoxide, mercuric acetate, potassium chlorate, sulfuric acid, andsaturated bro- Each test sample was heated at a temperature of 40 C. forto hours followed by a further heating at 100 to 120 C. for two hours,and was then distilled at reduced pressure. In every instance, thedistillate was a stable light-colored inhibitor oil having gasolinegum-inhibiting properties at least equal to those of ordinary inhibitoroil.

It is to-be understood that the process of the invention is applicableto the treatment of inhibitor oil as prepared from settled tar from thedestruction distillation of any ligno-cellulosic substance, particularlyhardwoods, such as birch and maple, as'well as softer woods such ashemlock, and other like materials, including peat and rotten wood. Theprocess is ordinarily'applied to the inhibitor oil itself, or to amixture of all the fractions obtained by distilling settled tar underreduced pressure, excluding the lowest boiling fraction whichessentially comprises methanol products, water, and acetic acid.However, it is also within the scope of the invention to treat "settledtar or other substance containing the inhibitor oil with an oxidizingagent, and thereafter to distill the treated product to separate theimproved light-colored stable inhibitor oil of the invention.

Other modes of applying the principle of the invention may be employedinstead of those explained, change being made as regards the detailsdisclosed, provided the method or product stated in any of the followingclaims, or the equivalent thereof, be employed.

We claim:

1. The method which comprises subjecting the inhibitor oil derived fromthe tarry products of wood distillation to the action of an oxidizingagent, and separating the substantially unoxidized fraction from thetarry oxidation products, the product so obtained being light-colored,miscible with gasoline, and eifective as an inhibitor in preventing -gumformation in gasoline and like petroleum products.

2. The method of treating the inhibitor oil derived by distillation fromthe tarry products of wood distillation, which comprises subjecting thesaid oil to the action of a small proportion of an oxidizing agent, anddistilling the treated product, to recover as distillate a light-coloredoil, miscible with gasoline, and effective as an inhibitor in preventinggum formation in gasoline and like petroleum products.

3. The methodof treating the inhibitor oil derived by distillation fromthe tarry products of wood distillation, which comprises subjecting thesaid oil to the action of a small proportion of an inorganic oxidizingagent and distilling the resulting product, to recover as distillate alightcolored oil, miscible with gasoline, and effective as an inhibitorin preventing gum formation in gasoline and like petroleum products.

4. The method of treating the inhibitor oil derived by distillation fromthe tarry products of wood distillation, which comprises subjecting thesaid oil to the action of a small proportion of a gaseous inorganicoxidizing agent, and distilling the resulting product, to recover asdistillate a light-colored oil, miscible with gasoline, and effective asan inhibitor in preventing gum formation in gasoline and like petroleumproducts.

5. The method of treating the inhibitor oil derived by distillation fromthe tarry products of wood distillation, which comprises subjecting thesaid oil to the action of a small proportion of a volatile liquidinorganic oxidizing agent, and distilling the resulting product, torecover as distillate a light-colored oil, miscible with gasoline, andeffective as an inhibitor in preventing gum formation in gasoline andlike petroleum products.

6. The method of treating the inhibitor oil derived by distillation fromthe tarry products of wood distillation which comprises heating the saidoil at a temperature between 70 and C. and passing air therethrough, andthereafter distilling the treated oil to recover as distillate a.light-colored oil, miscible with gasoline, and effective as an inhibitorin preventing gum forma: tion ingasoline and like petroleum products.

'7. In a method of treating the mixture of all the fractions obtained bydistilling settled tar" under reduced pressure except the lowest boilingfraction essentially comprising methanol prod ucts, water, and aceticacid, said mixture of fractions containing inhibitor oil, the stepswhich comprise subjecting the said mixture to the action of an oxidizingagent, and thereafter fractionally distilling the treated mixture torecover the fraction having an atmospheric boiling range of 220 C. to320 C., this fraction being a lightcolored oil, miscible with gasoline,and effective as an inhibitor for preventing gum formation in gasolineand like petroleum products.

8. The method of treating the tarry mixture derived from the destructivedistillation of wood and known as settled tar, said mixture containinginhibitor oil, which comprises subjecting the said mixture to the actionof an oxidizing agent, and thereafter fractionally distilling thetreated mixture to recover the fraction having an atmospheric boilingrange of 220 to 320 C., the said fraction being a light-colored oil,miscible with gasoline, and effective as an inhibitor for preventing gumformation in gasoline and like petroleum products.

ALFRED A. CAMlH-LI. MALCOLM K. JOHNSTON.

